Flood Risk Assessment


Flood Risk Assessment - England

In England, the requirements for a Flood Risk Assessment are detailed within the National Planning Policy Framework and Planning Practice Guidance which set out the Government’s national policies on different aspects of land use planning in England.

The Government produced Planning Practice Guidance document which is a web browser based document, the section relating to Flood Risk and Coastal Change can be viewed here.

The National Planning Policy Framework makes it mandatory for the Local Planning Authority to consult with the Environment Agency on planning applications for sites over one hectare in size or that are located in Flood Zones 1, 2 and 3.

The Environment Agency enforces the National Planning Policy Framework and has powers to challenge the Local Planning Authority over development applications in the flood plain.

The National Planning Policy Framework stresses that there is an increasing body of scientific evidence that the global climate is changing as a result of human activity. The impact of climate change at a regional level is likely to be variable: for the UK, projection of future climate change suggests that more frequent, high intensity rainfall and periods of long-duration rainfall of the type responsible for the 2007 floods could be expected. As a result, the Environment Agency , local authorities and local water authorities require flood and drainage data to be growthed over the lifetime of a development to take into account for the effect of climate change on flood risk.

The Environment Agency Flood Zones have been produced using a flood model known as JFLOW. JFLOW has been used to produce the 1% (1 in 100 year) and 0.1% (1 in 1000 year) flood outlines. The Environment Agency acknowledges that the JFLOW method is generalised and does not take flood defences into consideration. As such, the flood outlines produced by JFLOW can only be taken as a rough guide, showing where more detailed flood risk assessments are required.

The UK Government has put together a very useful website 'Flood map for planning', this flood map gives a broad indication of what flood zone a general area could be within and gives an indication on the likelihood of a Flood Risk Assessment being required to accompany a Planning Application for development.

Sanderson Associates has all the expertise and experience needed to challenge and in some cases correct the Environment Agency's flood maps should there be any doubt as to the flood zone allocation of a particular site. Flood zone correction often requires detailed flood modelling. We would usually recommend that a Desktop Flood Risk Assessment is first carried out in order for us to assess what type of modelling will be required and how much it will cost. Further information can be found on our flood modelling page.

We have extensive experience of completing Flood Risk Assessments which are fully compliant with the National Planning Policy Framework with a high success rate. We offer three levels of Flood Risk Assessment in line with the National Planning Policy Framework call us on 01924 844080 or complete our secure on line form to obtain our competitive fee proposal.

Flood Risk Assessment Level 1 – Screening Study

This report will provide a general indication of the potential flood risk to the site and identify whether there are any flooding or surface water management issues that may warrant further consideration or may affect the feasibility of a development. The purpose of a Level 1 Screening Study is to ascertain all sources of flood risk and whether any further work in the form of a Level 2 Flood Risk Assessment (Scoping Study) or Level 3 Flood Risk Assessment (Detailed Study) is required. It may also confirm that the site is at low risk of flooding from all sources and that no further assessment is required. The Level 1 report also covers the requirements for small scale extension works that meet the criteria set out in standing advice notes.

Flood Risk Assessment Level 2 – Scoping Study:

This report will provide qualitative appraisal of flood risk posed to a site and potential impacts will have on flood risk elsewhere. It will involve the production of a Flood Risk Assessment Scoping Study Report including possible measures to reduce flood risk for submission to the Environment Agency for comment/approval, all in accordance with the National Planning Policy Framework and associated Planning Practice Guidance.

Flood Risk Assessment Level 3 – Detailed Study:

A level 3 Flood Risk Assessment would be undertaken if the Environment Agency Agency (or other relevant environmental body) require further quantitative analysis to assess flood risk issues relating to the proposed development site e.g. Catchment Analysis, Hydraulic calculations or Flood Modelling may be required (if flood levels are not already available).

Production of a detailed Flood Risk Assessment may include catchment analysis, hydraulic calculations and modelling to quantify the potential flood risk to the site along with off-site flood risk impacts and determine appropriate flood risk mitigation measures.

Require a Flood Risk Assessment?

Sanderson Associates have enjoyed over 37 years in business, our Flood Risk Team have extensive experience completing Flood Risk Assessments in support of our clients major and minor developments throughout the whole of the UK.

We would be pleased to provide you with our competitive fee proposal for a Flood Risk or Flood Consequence Assessment, please call us on 01924 844080 or click here to complete our secure online form.

Flood Risk Assessment, National Planning Policy Framework, NPPF
Environment Agency, JFLOW
Desktop Flood Risk Assessment, Modelling, JFLOW, HEC-RAS
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